Let's step back for a moment...
Broadly-speaking, there are a couple of ways to interpret just about any flag
1. "this specific thing that's being flagged is problematic in some way"
2. "the context in which this flag was raised is problematic in some way"
Now, most flags have some element of both, but tend toward #1
The obvious exception being "other" / "in need of moderator attention/intervention", in which the text typed by the flagger is used to establish context and might therefore indicate a problem that is much greater in scope than the post/comment being flagged or even entirely separate from what is flagged.
But, a good moderator should be able to interpret a flag in order to determine what is needed in each case. For example, a spam flag might also result in the destruction of the author of the post, or a rude flag might trigger a warning or suspension.
Comment flags are immediately problematic because - with the exception of "other" - they carry very little context by default.
A rude comment may be just that - someone being unnecessarily crass in their method of communication - or it may be a part of a larger argument full of crass and insulting language.
But, in the flag queue, you're given nothing but the text of the comment and the name of the flag to help you judge this.
There are 7 comments in that thread in total
Including the one to which the flagged comment replies
None of that is indicated directly in the UI, so a moderator handling this has to guess
This is usually not a crippling problem for rude/offensive/whatever
But "obsolete" implies something else - namely, that the comment was important at some point but now is no longer.
The UI is the same though - both for the flagger, and for the moderator handling the flag.
There's still no way to provide context, nor is implicit context exposed
In busy threads / questions, this actually gets even worse if you click through to the question, since comment flags aren't shown inline... So "don't handle comment flags from the mod queue" is problematic not only because it greatly increases flag handling time, but also because it may not even help.
One might expect breaking off "obsolete" into a separate flag type to improve this, but it doesn't appear to do so in the common case
For starters, flaggers routinely use it in cases where no context is needed ("noise"), so there's a heavy cost to adding additional steps to processing them.